The amino acid esters are long chain compounds with nutritional (Paquet, A. Can. J. Biochem. 1980, 58, 573-576) and surfactant applications (Kawase, T.; Nishioka, Y.; Oida, T. J. Oleo Sci. 2010, 59, 191-201). The synthetic routes for such kind of compounds are pretty limited and required the use of short-chain, liquid alcohols as raw materials (Brook, M.; Chan, T H. Synthesis -Stuttgart 1983, 201-203); but fail to use solid alcohols as is the case of fatty alcohols required to obtain compounds of amphiphilic nature.
Conventional synthesis methods are very aggressive for the environment because they use very strong and corrosive acid catalysts (Yang, Q.; Wang, X.-J.; Li, Z Y; Sun, L.; You, Q D. Synth Commun. 2008 38, 4107-4115; Penney, C. L; Shah, P; Landi, S J. Org Chem. 1985, 50, 1457-1459), very toxic and dangerous reagents such as p-toluenesulfonyl chloride (Arai, I.; Muramatsu, I J. Org Chem. 1983, 48, 121-123), diazomethane (Leyendecker, F.; Jesser, F.; Laucher, D. Tetrahedron Lett. 1983, 24, 3513-3516) or ortho esters (Gibson, S.; Romero, D.; Jacobs, H K; Gopalan, A S. Tetrahedron Lett. 2010, 51, 6737-6740).
It is common that the synthesis reactions require multiple steps (protection, esterification and deprotection) obtaining products with low yield (Zhao H.; Song Z.; Cowins J V.; Olubajo, O. Int. J. Mol. Sci. 2008, 9, 33-44; Sureshbabu W.; Kantharaju; Krishna G C. Int. J. Chem. B. 2007, 46, 1466-1469) or by using an inert atmosphere (Sathe M.; Kaushik M P. Catal. Commun. 2006, 7, 644-646).
Recently, a strategy of synthesis in one step by microwave irradiation and where a yield of about 60-80% is obtained by using an excess of alcohol (Cerón-Camacho, R.; Aburto, J.; Montiel L. E.; Flores, E A.; Cuellar, F.; Martinez-Palou, R. Molecules, 2011, 16, 8733-8744).
Compared to such method, the present invention turns out to be attractive because the use of a microwave reactor is avoided, the reagents are used only in stoichiometric ratio and with a slight excess of acid functions both as catalyst and reactant. Therefore, the reaction is easily scalable and product performance is roughly comparable and even higher than 80% using both short as long chain alcohols.